North Korea warned Japan Friday that its launch of two reconnaissance satellites earlier in the day could spark an Asian arms race. Japan's first spy satellites are primarily meant to keep watch over North Korea, amid growing concerns over that country's nuclear ambitions.

North Korea issued a swift denunciation Friday, criticizing Japan for sending its first spy satellites into orbit hours earlier. A spokesman for the North's Foreign Ministry told the official Korean Central News Agency that Japan will be held responsible for starting an arms race in Northeast Asia. He said the satellites posed a threat to North Korea.

He also claimed that Japan had wantonly violated a joint declaration, signed last year, on improving the two nations' strained ties. Under that pact, North Korea agreed to extend its existing moratorium on missile testing beyond 2003.

Pyongyang's last such test came in 1998, when it launched a missile over Japanese territory and into the Pacific Ocean, to the great surprise of Tokyo and Washington. The Japanese are now watching nervously to see if Pyongyang will test another ballistic missile in response to the satellite launch.

The 1998 test prompted Japan to jump start a program to develop its own surveillance capabilities, instead of having to rely on U.S. intelligence data.

On Friday, Japanese television showed an H-2A rocket lifting off at 10:27 a.m. local time from a remote launch site 1,000 kilometers southwest of Tokyo. The rocket soared through a brilliant blue sky and trailed a plume of smoke as it ferried Japan's first spy satellites into space.

Hundreds of police circled the launch site, and coast guard ships patrolled nearby waters. They were there as a precaution against possible terrorist attacks linked to the U.S.-led invasion of Iraq, which Japan supports, and to ward off any possible sabotage by North Korea.

Japanese officials tried to offer reassurance that the launch was not meant to threaten Pyongyang.

Government spokesman Yasuo Fukuda says other countries have satellites in orbit, and Japan has fallen behind them. He says Japan will develop this and other strategies for gathering information, but the aim is not to attack or invade other nations.

Japan's space agency bills the satellites as multipurpose, but their primary use will be to gather intelligence on North Korea. Pyongyang has alarmed Tokyo over the past several years, and especially in the last six months, with a series of acts that Tokyo views as highly provocative. They include restarting banned nuclear facilities and withdrawing from the nuclear Non-Proliferation Treaty.